This invention relates to a tensioner which provides a fixed tension to a chain or timing belt which drives a cam shaft of an engine of a car.
The tensioner is generally used as a chain or a belt tensioner to an engine. The tensioner operates to push the chain or the belt in a certain direction directly or indirectly so as to maintain a fixed tension when the chain or the belt extends and slackens by friction.
Such tensioner is adapted to insert into a casing by screwing the rotary body and an urged body to energize the rotation of the rotary body with a spring force and change the rotation force of this rotary body to a propelling force of the urged body to advance the urged body from the casing. The top end of the urged body always urges the chain or the like, thereby maintaining a fixed tension.
FIG. 8 shows a traditional example of this tensioner wherein a rotary body 3 and an urged body 4 are inserted into a cavity 2 formed in a casing 1 in a screwed state and a torsion spring 5 is outwardly inserted into the rotary body 3. The screwing of the rotary body 3 with the urged body is performed by providing a male portion 3a at the top end side (left side) of the rotary body 3, while providing a female portion 4a at the inner surface of the urged body 4. The urged body 4 is inserted through an opening in urged body 4. The urged body 4 is inserted through an opening in a bearing 6 which is prevented from being withdrawn by a circlip inserted into the top end portion of the casing 1, and rotation of the urged body 4 is prevented by making it and the bearing opening non-circular. Further, one end 5a of the spring 5 inserted outwardly through the rotary body 3 is inserted into a long groove 1a and the opposite end (not shown) is inserted into the rotary body 3, thereby energizing the rotation of the rotary body 3. In such a construction, the rotary body 3 rotates by the spring force, and this rotation force is transmitted to the urged body 4 screwed with the rotary body 3. In this case, since the rotation of the urged body 4 is restrained by the bearing 6, the rotative force thereof is changed to a propelling force to advance the urged body 4 is restrained by the bearing 6, the rotative force thereof is changed to a propelling force to advance the urged body 4 from the casing. Since the top end portion of the urged body 4 abuts against the chain or the belt (not shown) directly or indirectly, this member is maintained at a fixed tension by the advancement of the urged body 4. The inner cavity of such tensioner is sealed and a lubricant oil is sealed therein, thereby providing a smooth operation. This closely sealed construction will be described as follows.
The numeral 8 is a seal bolt screwed with the base portion (right portion) of the casing 1, said seal bolt engaging a seal ring 9 and a washer 10 thereby sealing off the base portion of the casing 1. On the other hand, a cap 11 is inserted at the top end portion of the urged body 4 and a boot 12 is bridged between the cap 11 and the casing 1 for covering them whereby the sealing of the top end portion of the casing is performed. Accordingly, the casing 1 is closely sealed by the seal bolt 8 and the boot 12.
In such a tensioner, the spring 5 is twisted to store energy at the time of assembly. At the time of maintenance and the conveyance before assembling of the device, there necessitates the locking of the rotation of the rotary body 3 against the energy of the spring 5. For this purpose, there is provided a stopper mechanism which performs a locking of the rotation. The stopper mechanism is provided by a stopper hole 13 formed in the base side of the casing in a right angular direction to the axial direction, and a pin shaped stopper member 14 inserted into the stopper hole 13. A slit 15 to be engaged by a winding or clamping tool (not shown) such as a screwdriver is formed at the base of the rotary body 3. The slit 15 is used for winding the spring at the time of assembling the tensioner. In other words, the winding of the spring 5 is performed by inserting the tool from the base portion side of the casing 1 in a removed state of the seal bolt 8, and by rotating the rotary body 3 by engaging the top end of the tool with the slit 15 of the rotary body 3.
After winding the spring 5, locking of the rotation of the rotary body 3 against the spring force of the spring 5 is performed by inserting the stopper member 14 into the stopper hole 13 of the casing 1 and a slit 15 of the rotary body 3. Further, after assembling the tensioner to the device, the rotary body 3 rotates by the spring force by pulling out the stopper member 14, thereby to maintain tension of the chain or the belt caused by the advancement of the urged body 4.
However, the stopper mechanism of the known tensioner is only for locking the rotary body 3 against rotation. Accordingly, this mechanism is composed only of the stopper member 14 which fits into the stopper hole 13 of the casing 1. In such a construction, not only at the time of operation of the tensioner wherein the stopper member 14 is drawn out from the stopper hole 13, but also in a state wherein the stopper member 14 is inserted into the stopper hole 13, the lubricant oil is apt to leak from the stopper hole. The amount of leakage increases with vibration of the tensioner during conveyance of the tensioner or in maintenance thereof. The leakage of the lubricant oil decreases the smoothness of operation of the tensioner.
The object of this invention, therefore, is to prevent the leakage of the lubricant oil not only at the time of the operation of the tensioner, but also during conveyance or maintenance and to provide a tensioner which has enhanced lubrication.